The present invention relates to a switching center for a mobile cellular network and a method for the operation thereof, in particular the present invention relates to a switching center for a mobile cellular network enabling temporary wireless local loops in cellular mobile networks.
Basic sub-systems for the architecture of cellular mobile networks shown in FIG. 12 are a base station sub-system BSS, a switching center SC, a home location register HLR, and a visitor location register VLR, respectively. Neither the base station sub-system BSS nor the switching center SC are in direct contact with external networks, e.g., a public switched telephone network PSTN, and integrated services digital network ISDN, and a public land mobile network PLMN, e.g., a global system for a mobile communications GSM, a digital cellular network at 1,800 MHz DSC 1,800 or a personal communication system PCS. To link these networks, there is provided a gateway service switching center or switch that serves to determine specific locations of a mobile station MS in the cellular mobile network and to route calls towards this mobile station MS.
To this end, the switch is connected to a functional unit called home location register HLR storing subscriber information and mobile information to allow incoming calls to be routed to a mobile station MS. Thus, any administrative action through the network operator with respect to mobile station data is carried out in the home location register HLR.
To route a call to the mobile station MS, the switch, e.g. the GMSC in the GSM network, is also connected to a switching center SC through which the mobile station MS finally obtains a service. The switching center performs the necessary switching functions required for mobile stations MS covered thereby. Further, the switching center SC monitors the mobility of its mobile stations MS and manages necessary resources to handle and update the location registration procedures.
As shown in FIG. 12, the cellular mobile network comprises a plurality of switching centers SC covering a predetermined number of basic cells for an area wherein a mobile station MS may roam. Heretofore, each switching center SC is connected to a visitor location register VLR. This visitor location register VLR is a functional unit that dynamically stores mobile station information, e.g., location area in case the mobile station MS is located in the area covered by the visitor location register VLR. In case a roaming mobile station MS enters an area assigned to a specific switching center SC, the switching center SC informs the associated visitor location register VLR about the mobile station MS.
Further, the base station sub-system BSS corresponds to physical equipment providing radio coverage to prescribed geographical areas known as cells and shown as hexagonal geographical regions in FIG. 12. Each base station sub-system BSS contains equipment required to communicate with the mobile station MS. Functionally, a base station sub-system BSS provides a control function carried out by a base station controller BSC and a transmitting function performed by the base transmitter station BTS. Thus, the base transmitter system BTS corresponds to a radio transmission equipment and covers a single cell. To the contrary, the complete base station sub-system BSS serves several cells because it may comprise a plurality of base transmitter systems BTS.
Therefore, contrary to a fixed network such as the public switched telephone network PSTN, where the connection between the subscriber in the next network node called xe2x80x9clocal-loopxe2x80x9d is fixed and rent by the subscriber to avoid the access of further subscribers thereto in mobile cellular networks the subscription does not include the connection to the closest network node, i.e. the next base station sub-system BSS.
Even more important, in cellular mobile networks, the bandwidth or equivalently the available communication capacity in one cell is limited. In case a mobile user needs access to communication capacity, e.g., for a call or a service at a specific time, it may not be guaranteed that this communication capacity is actually assigned to the subscriber. The reason for this is that during specific times there may exist congestion in the cell where the user is currently located. Further, due to the increasing number of subscribers to cellular mobile networks and to the significant increasing use services requiring ever more bandwidth than currently existing services, this situation may even arise more often in the future.
While one could think of using directly the priority handling provided for an existing cellular mobile networks such as GSM, this could lead to different treatment of subscribers therein which is clearly not desirable for the operators as well as the subscribers. One reason is that the use of priorities effective over the complete network at any time and any place will beyond doubt lead to problems, since, firstly, in case of congestions within overloaded cells everybody would simply increase his priority to get communication capacity and, secondly, with many high priority users there would exist too many subscribers to higher or even highest priority. In conclusion, in today""s mobile cellular networks there exists no possibility for the subscribers to reserve communication capacity such that each subscriber has the same opportunity to carry out such a reservation and an overall continuous throughput in the mobile cellular network is nevertheless maintained.
In view of the above, the object of the invention is to achieve an increased subscriber accessibility in a mobile cellular network.
According to the present invention, this object is achieved through a switching center for mobile a mobile cellular network, comprising interface means adapted to establish at least one communication channel between said switching center and at least one mobile station roaming in at least one cell of said mobile cellular network, assignment means adapted to change a communication channel assignment at said interface means upon an assignment request, each assignment request specifiying at least a target position and a communication capacity change, respectively, and communication capacity reservation means adapted to reserve a specific communication capacity to at least one target position during a prespecified period of time upon receipt of a reservation request.
Therefore, the inventive switching center enables the subscriber of the mobile cellular network to reserve communication capacity in a specific area and within a specific time frame. Typically, the subscriber initiates a request for a communication capacity using a message to the switching center, e.g., using USSD and SMS, respectively, wherein the communication capacity, one or more target positions for which the reservation is to be carried out and also the specific time frame is defined. Using this specific request information, the switching center blocks the requested communication capacity for other subscribers in case the communication capacity is available.
According to the preferred embodiment, the communication capacity reservation means comprises a data base means adapted to store at least the reserved communication channel capacity, the communication channel target positions, and the prespecified period of time for each reservation request. The provision of the data base means allows a very simple evaluation of each request submitted to the switching center, since requests previously submitted thereto can easily be checked on.
According to a further preferred embodiment of the present invention, the data base means also stores a priority value which is effective in the range of the target positions or in other words only in a small part of the mobile cellular network and which is a measure of probability that said assignment means is activated at the beginning of the prespecified period of time in accordance with the reservation request. This embodiment of the invention is particularly well adapted to situations where a plurality of requests for communication capacity are submitted to the switching center, each of which may not be acknowledged due to already existing reservations. Using priority values, the service provider has the opportunity to give preference to important customers, if necessary.
According to a further preferred embodiment of the present invention, the communication capacity reservation means further comprises a request checking means adapted to check whether a submitted request can be acknowledged or not. This evaluation can be carried out using a plurality of criteria such as available communication capacity for a cell, a maximum acceptance time between submission of a request and acknowledgment thereof, and the authorization of a subscriber to submit such a request, respectively. The last case can be related to a roaming subscriber which, e.g., in accordance with existing subscription conditions may only reserve reservations in, e.g., his home public land mobile network.
According to a further preferred embodiment of the present invention, the switching center also comprises location mapping means adapted to map a geographical information specified in a request into the at least one target position. Therefore, according to the present invention, it is taken into account that the subscriber usually is not aware of the cell-ID of the cell where he is currently roaming but more or less only is thinking of, e.g., specific cities, areas, street names, and so forth. However, the inventive location mapping means enables the subscriber to specify the area for which he needs a communication capacity reservation in the more accessible terms of locations, e.g., the Aachen main station or a specific place of business, which may then be transformed cell-IDs through software processing a relationship between these location informations and the cell-IDs.
According to a further preferred embodiment, the location mapping means further processes routing information specified in a request. This embodiment reduces the burden on the subscriber to specify at which positions at what time he needs a communication capacity reservation. The subscriber simply specifies his route starting point and route ending point as well as his travelling speed and expected required communication capacity. From this, the location mapping means derives all positions along the specified route. Further, the start time and end time for each cell along the path are derivable from the start time for the first cell and the cruising speed of the subscriber. In addition, the current location may be derived during an ongoing call using, e.g., cell Ids or even exact positions. Furthermore, reservations in cells a subscriber has left may be released.
According to another aspect of the present invention, there is provided a method to reserve communication capacity between at least one switching center in a cellular mobile network and a mobile station roaming in at least one cell of said cellular mobile network, said method comprising the steps receiving a request for communication capacity between said switching center and said mobile station, deriving all cells covered by said switching center and being affected through said received request, determining a match between a communication capacity assignment profile and said requested communication capacity for all affected cells, and reserving a communication channel according to said requested communication capacity between said switching center and said mobile station at a start time prespecified in said request for communication capacity.
Therefore, the inventive method relies on the concept of a communication capacity assignment profile for each cell in a cellular mobile network specifying for each time the amount of communication capacity previously reserved. Using this approach, the admissibility of a further submitted request can be evaluated simply through a scan of all times where the communication capacity assignment profile of the cell changes.
Overall, the present invention provides a subscriber to a cellular mobile network with the possibility to rent needed communication capacity for a specific time frame. This is particularly useful in case where the mobile subscriber wants to be reachable within a specific time frame at a specific cell in accordance with a specific bandwidth. In another case, the subscriber may want to set up a connection with a specific communication capacity during a specific time frame and a specific cell. With the described functionality, the inventive cellular mobile network guarantees the communication capacity in the selected cell within the selected time frame in compliance with the mechanisms provided for in fixed networks.